The ultimate aim of this project is to establish a mechanism of facilitated interface catalysis in a pancreatic lipase-colipase system. Specific aims include studies of phase-transition changes in micelle structure as a result of colipase and lipase binding using an array of fluorescent probes which include DPH, DPE, perylene and 12-(9-anthoryl) stearate each with individually variable probe capabilities. Energy transfer experiments will be carried out between horse colipase (which contains a single active site tryptophanyl residue) and the bound fluorophores. Additional phase-transition and energy transfer experiments will be performed on nitrated porcine colipase which will be reduced to the aminotyrosine derivative and studied as such. Further, the amino acid derivative will be reacted wih dansyl chloride to produce yet another fluorescent probe system. Studies of both the binary colipase-micelle and the ternary system with lipase will yield important information as to the nature of the interface catalytic system. In addition, cross-linking experiments using an insoluble bifunctional reagent dissolved in the lipase substrate, tributyrin, will be performed to provide basic structural evidence for the topography of the ternary system. Information provided by these studies will be applicable to lipoprotein-lipase interactions in fat metabolism and therefore relate to plasma protein catabolism and atherosclerosis.